This application claims the benefit under 35 U.S.C. xc2xa7371 of prior PCT International Application No. PCT/JP97/03497 which has an International filing date of Oct. 1, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
The present invention relates to a medical anesthetic needle including an inner needle, having a pencil-pointed tip, and a tubular outer needle, having the inner needle inserted thereinto and therethrough.
Conventional inner needles, having a pencil-pointed tip (4), of anesthetic needles, are inserted into and through a straight-tubular outer needle having its fore-end section formed in a tapered shape, tapering off towards the end thereof, i.e., a hollow, truncated conical shape. The fore-end part of the outer needle was deburred, but relatively sharp, thus resulting in patients often feeling pain when the needle is inserted into the body. An anesthetic needle for easing such pain is disclosed in Japanese Utility Model No. 3018360 where the fore-end section of a tubular outer needle has the edge formed to be round on the right-angled cut fore-end face thereof.
With an anesthetic needle with the fore-end section of a tubular outer needle thereof having the edge formed to be round on the right-angled cut fore-end face, the patient""s pain when pricked with the needle was eased somewhat in comparison with an anesthetic needle having a sharp-edged fore-end section of its tubular outer needle. However, the extent of its pain reduction was not enough.
The cause of a patient feeling pain when pricked with a needle, even though the fore-end part of the tubular outer needle is formed to be round, is the presence of a gap between the fore-end section of the outer needle and the inner needle. The difference between the outer diameter of the inner needle and the inner diameter of the outer needle is about 0.05 to 0.1 mm, depending on the needle size. Thus, a gap having a maximum width of 0.05 to 0.1 mm may be formed since the inner needle tends to be decentered relative to the outer needle when needling. When a patient""s nervous tissue is nipped in this gap, the patient feels pain.
An object of the present invention is to provide a medical anesthetic needle including an inner needle having a straight needle shape, and a pencil-pointed tip, and having an outer needle with a straight tubular shape, having the inner needle inserted thereinto and therethrough, wherein the medical anesthetic needle is capable of sufficiently easing the enough a patient""s pain when needled.
To accomplish this object, a medical anesthetic needle, is provided, which includes an inner needle with a straight needle shape and a pencil-pointed tip, and an outer needle with a straight tubular shape and having the inner needle inserted thereinto and therethrough, wherein the fore-end part of the outer needle is formed in a tapered shape, tapering off towards the end thereof, i.e., a hollow, truncated conical shape or the like. Furthermore, the foremost section of the fore-end part is formed as a foremost-end part so that the minimum inner diameter of the foremost-end part is smaller than the outer diameter of a section of the inner needle excluding the tip, i.e., the main body of the inner needle.
The foremost-end part of the outer needle may be applied only with deburring so that the edge of its right-angled cut fore-end face is left sharp. If required, the foremost-end part may have the edge of its right-angled cut fore-end face worked to be round.
With an anesthetic needle of the present invention, when a patient is pricked with a needle, the foremost-end part of its outer needle is located on the circumferential surface of either a section near the root of the tip or the main body of the inner needle where the outer diameter of the inner needle is equal to or greater than the minimum inner diameter of the foremost-end part of the outer needle. Thus, no gaps, are formed at all between the foremost-end part of the outer needle and the inner needle. Therefore, the patient is not likely at all to feel pain caused by the patient""s nervous tissue being nipped between the outer and inner needles.